A lot of Spykers went to US dealers but some of these were not sold to a US customer and returned to Spyker and went to other dealers in Europe or the Middle East. And like F Spider mentioned, quite a few were exported from the US. So it's difficult to determine how many there still are in the US but 40% and 100 cars as mentioned in the above post is quite accurate as 97 out of 188 known cars in our registry (ex racecars and ex Ailerons) initially went to the US.

Very interesting info about the engine indeed: "5 litre V8 610Hp" and "very special company" and "even more high-end than we are" and "6 speed Cima gearbox". Taking the above mentioned specs. into account I would say Koenigsegg!

So, what makes that a Koenigegg engine? I can only find 1000+ HP engines and 7 speed sequential gearboxes. Am I missing something?

I was wondering that too - maybe if you take off the turbos (good) then you get back to that power level... But I think there are other 5 liter V8's that could be candidates. But higher end than Spyker???

"5 litre V8 610Hp": Koenigsegg uses a 5 litre V8 with compressors and these engines deliver over 1,000 Hp, close to 1,500 even, which would be way too much for the Preliator as that's not a hyper car but more a sportscar. Without compressors the Koenigsegg engine could well deliver 610 Hp. To be honest I don't think there are too many 5 litre V8's that deliver that amount of power.
"very special company": There are not that many special companies in my opinion but Koenigsegg would qualify in my book.
"even more high-end than we are": That means a company that has made less than 250 cars and engineered their own engine. Koenigsegg complies to that and I can't think of any other company.
"6 speed Cima gearbox": Koenigsegg also uses Cima gearboxes so the Cima gearbox will fit the Koenigsegg engine and will be a good match.
It's not definitive but all these clues combined, I think it could very well be Koenigsegg but time will hopefully tell!